Cell surface heparan sulfate proteoglycans are widely distributed throughout animal tissues, and are involved in critical cell functions such as cel-cell and cell-extracellular matrix interactions. Their interactions with a variety of molecules including growth factors, viruses, and extracellular matrix proteins, have important biological functions. The purpose of this project is to study the metabolism of cell surface heparan sulfate proteoglycans with focus on mechanisms involved in their endocytosis and subsequent intracellular processing. Topics of present interest include: (1) characterization of the intracellular trafficking and processing pathway for the dermatan sulfate proteoglycan which may enter the nuclear compartment; (2) further development of the procedure to isolate quantitatively and purify nuclei from UMR 106 osteoblastic cells and granulosa cells; and (3) define the intracellular subcompartments where the intercalated heparan sulfate proteoglycans are selectively degraded.